The invention relates to a safety monitoring device to be located at the entrance of a magnetic resonance (MR) examination room. The safety monitoring device assesses whether it is safe for the subject of interest, i.e. a patient, to undergo a MR examination in a MR examination room, notably in a electro-magnetic field region of a MR examination system located within the MR examination room.
State of the art in safety for performing examinations using an MR examination system is an interview with the patient prior to the examination to identify if the patient is free of components which might cause problems during the examination or which might cause harm to the patient. Hence, the safety of the MR examination depends on the information provided by the patient, and this method has a low reliability.
To improve safety, it is known e.g. from WO 2013/001292 A2 to use an apparatus for detecting ferromagnetic objects located on or in a patient, who is to be examined subsequently using a MR examination device. The apparatus comprises a magnetic sensor, which in use measures an ambient magnetic field or gradient within an examination space, and a warning device. Accordingly, ferromagnetic objects a patient may inadvertently be carrying are detected and a respective warning is generated. Such objects may cause degradation in the MRI image and require the patient to be re-scanned. Examples of objects in this category include hair/bobby pins, wrist-watches and jewelry clasps and pins.
Magnetic materials are not the sole reason of concern in MR imaging. Also resonant radio frequency (RF) structures can lead to potentially unsafe situations. Such structures can be stents, passive implants, or leads for active implants. None of these are typically ferromagnetic, and will go undetected by the above apparatus. Nevertheless, these structures can be stimulated by the RF fields applied during MR examination, which may cause harm to the subject of interest. Also imaging quality of the MR examination may suffer from the presence of resonant RF structures. Presence of such resonant RF structures could be detected when the subject of interest is already located inside the examination space of the MR system. Nevertheless, if a resonant RF structure is detected only at that time, the scan strategy must be adapted, or the patient has to be removed and MR scanning cannot be completed. At least, the cause of the RF interference must be identified, and potential MR conditions have to be retrieved, e.g. from an implant database in case the RF resonance is caused by an implant. This reduces the efficiency of the MRI scanning process and the entire department workflow for MR scanning.
MR examination systems are usually very cost intensive. Therefore, it is desired to handle safety questions separate from the MR examination systems to avoid halts of the MR examination system and to improve a workflow which enables a continuous operation of the MR examination system.